Year	Percent
1960	49.87486
1961	49.92284
1962	49.18083
1963	47.51292
1964	47.2434
1965	49.06616
1966	48.03328
1967	45.83876
1968	44.42645
1969	45.36959
1970	51.02812
1971	54.04524
1972	54.49765
1973	58.59658
1974	60.48771
1975	70.61594
1976	71.87104
1977	73.28726
1978	73.65537
1979	65.2178
1980	71.76304
1981	58.32648
1982	50.2411
1983	53.05758
1984	49.75668
1985	48.37572
1986	53.09797
1987	54.7545
1988	54.2744
1989	54.37623
1990	53.28291
1991	49.37254
1992	48.20294
1993	48.28488
1994	46.16985
1995	45.29539
1996	41.0372
1997	38.11996
1998	38.25105
1999	34.78598
2000	27.50911
2001	27.85024
2002	23.43343
2003	24.50702
2004	21.67035
2005	25.07494
2006	24.03493
2007	22.27811
2008	21.3846
2009	34.87286
2010	32.86801
2011	28.96925
2012	27.17726
2013	26.03032
2014	24.81998
2015	23.47237
2016	22.66032
2017	23.45884
2018	23.25029
2019	22.94551
2020	23.92903
2021	23.8418
2022	24.01172